EcoDiesel Engine Rebuild log

Main Bearings:

Part Number: MB4556SX (King Bearing)

I am going to start with the mains because it's what I'm working on at the moment. Mopar does not sell these anymore (even though many sites are still listing them as available). They use a color-coding method for specifying bearings which is more common with newer vehicles, but was totally new to me. To make matters worse, there are no specific tolerances called out, but rather a tolerance stack is developed by using the specified combination of bearing colors (top and bottom can be different colors). The bearing codes are stamped to the front of the block, and the front crank counterweight.

All this said, there is a way to decrypt the Mopar specification table, and after backward-calculating their data, I ended up with a range of 0.0024"-0.0039" for the mains. I'm hoping to validate this through feedback from others as well as my own hands on experience with the engine I'm working on.

I ordered mains from Summit racing at a reasonable price ($103), and received them today. Here are the factory and King bearings side by side (factory is the darker one):


I went ahead and took some shell thickness measurements and found the King bearing to be ever so slightly thinner (King bearing averages 0.0796" vs factory 0.0799").

Next, I put the new bearings in the engine with plastigage. I'd like to describe the procedure i used to see if anyone has any objections to it:

I'm used to engines with individual main caps, and always measure the mains one at a time. However, in the case of the ecodiesel, the bedplate has 29 bolts holding it together with a LOT of pressure. I decided to just put the plastigage on each of the mains and measure them all at once. The other "deviation" from what might otherwise be recommended is that I used the old main bolts (which are torque-to-yield), and tightened everything down per the spec. One could argue that this may result in a false reading, but what I found leads me to believe it is OK. I will be using new bolts for final assembly. After taking everything back apart, here are the measurements front to rear:

#1 Main: 0.0020"
#2 Main: 0.0015-0.0020" (was in between marks on the plastigage scale)
#3 Main: 0.0020"
#4 Main: 0.0020"

This is at the tighter end of the range I had calculated, however I am rationalizing that the RTV in-between the bedplate and block has to be at least 0.0005" thick.

That's it for now. I'll add more as time permits

That’s interesting that you just apply sealant between block and bedplate. It seems like depending on how much sealant you apply, your tolerances may vary. Maybe it’s a moot point, and what needs to be squeezed out will come out. On the Bmw N55 gasoline engine, they also use a bedplate. However there is a groove in the plate and block. After bedplate is installed, you apply sealant to this groove through a port on the side of the block.

I've been doing more research on the "colored bearing" approach to engine manufacturing. Based on what I've read, I've come to the conclusion that the different sized bearings are used to compensate for manufacturing variations by custom fitting each bearing half to each main on the block side rather than the crank side (this may be obvious to some, but I'm putting it out here for refutation by anyone who knows different).

If this is correct, then engines which originally had different upper and lower bearing colors would most likely need to be line-bored before using the King bearings. In the case of my engine, they were all "Blue", and all the mains were within a range of 0.0015"-0.0020", so I am going to proceed without line-boring.

I did call a local machine shop that works on Sprinter engines (Mercedes v-6 3.0 diesel) as well as a few ecodiesels, and they felt I was good to go with the clearances I measured.

Next will be either rod bearings or pistons (depending on which parts/tools arrive first)

RansomT said:

The motorcycle world has been using color coded bearings for several years. The cases are "supposed" to be used in machine sets, so that you don't mix the bearing colors. You measure the crank journal and match the bearing size to it. Then you check with plastigage and make changes as needed. The sizes of the different bearings and tollerances are so "small" that you really need multiple sets of bearings on hand to do the job right. If VM is mixing the bearing shell sizes at the factory, then that is an issue. Might be away for them to pushing through the manufacturing proccess of an engine that otherwise would be trashed/recycled.

Click to expand...

Most of the info I found was from the motorcycle sites

It's clear to me that they do mix colors on the same journal (at least for the mains). Take a look at the 2nd image below which is the crank from the 2nd motor I took apart. You can see it is stamped "BABA". I can't find a picture of the old block, but as I recall, it was stamped BBBB. The 3rd picture shows that they do have a spec for mixed Red and Blue (I'm guessing that is part of the reason they were sold individually). Also note, that the rod bearings were sold in pairs only.

Bottom line, I'm convinced that they built some engines with mixed colors on the same journal.

Rod Bearings

Part Number: CR6900SV

I received the rod bearings from Summit this past week. They look identical to the factory units.

When installed, the clearances came out as follows:


Here are the factory specifications for the rods:



Following the rule of thumb of 0.001" clearance per inch of journal diameter, I should be targeting ~0.0027" +/-, so most of my tolerances are on the tight side. Hopefully, the 5W/40 will still work OK.

Taking a quick break from the mechanical stuff for a moment, I wanted to share a cool hack that I came across recently that saved my several hundred bucks on a wire harness.

Whoever owned my truck previously must have panicked during the fire, and cut all the positive battery cables at the battery terminal (there are 7 total cables on this one junction!):





By using some of the techniques in this video: I was able to save the wire harness. The only thing I did differently was to put flux on the wires prior to crimping and wick solder into the joint. It turned out like this: